Asthma Subgroups: Allergic Bronchopulmonary Aspergillosis (ABPA)

Allergic Bronchopulmonary Aspergillosis (ABPA) is a very rare subgroup of asthma where asthma symptoms are coupled with a sensitivity to a fungus called aspergillus. Here is all you need to know.¹

Aspergillus Fumigatus

It’s a fungus, or mold, that’s hard to avoid as it lives in water, soil, dust, marijuana, some spices, and rotting vegetation, which includes dead and decaying trees, compost piles, and piles of dead leaves.²

They develop microscopic, easily “aerosolized,” spores that are inhaled into your deepest airways. They impact and adhere to the warm mucus lining of your respiratory tract, which provides an ideal environment for them to colonize.³

They are harmless to most people, although cause infections in those with compromised immune systems. These infections, called Aspergillosis, are considered invasive because the fungus invades and damages tissues. However, these infections are not what causes ABPA.^2,3

ABPA

This is whereaspergillus fumigatus colonize along the mucus lining of your nose, sinus cavities, throat, bronchi, bronchioles, and terminal airways. After prolonged and repeated exposure over the course of many years, your immune system develops a sensitivity to it.³

This is the same response that occurs with allergic asthma, so we can consider it a form of extrinsic asthma. This infection is considered non-invasive because it does not invade and damage tissues. Any damage that occurs is due to you own immune response to the fungus.⁵

Symptoms gradually develop over time, so it is usually not diagnosed until after the age of 50.^3,5

More information on allergic bronchopulmonary aspergillosis

Symptoms

Early symptoms may include a runny nose and sneezing. This may gradually progress to worsening asthma, increased mucus production, and coughing. Mucus may appear tan, brown, or be streaked with blood. It may become thick and hard to spit up, resulting in mucus plugs that further obstruct airways. Other symptoms include fever, unexplained weight loss, and malaise.^1-5

Statistics

About 25% of asthmatics are said to be sensitized to aspergillus fumigatus, although only about 2% of these develop ABPA. One study showed that as many as 75% of patients diagnosed with severe asthma who required “multiple” hospital admissions were sensitized to it.^3,4,7

It’s most common in people with asthma and cystic fibrosis who also have allergic conditions (atopy) such as allergic asthma, atopic dermatitis (eczema), conjunctivitis (allergic pink eye), food sensitivities (food allergies), or rhinitis (hay fever, nasal allergies). The incidence is the same in both women and men.^1-3

About 75% of those with ABPA have sinusitis. One theory speculates this may be due to some sort of “abnormal sinus anatomy.”³

Causes

Aspergillus fumigatus appears to be a very stubborn fungus. The initial immune response results in inflammation and increased sputum production, and this is an attempt to kill, trap, and have you cough up the spores. However, the fungus appears to be resistant to this, resulting in an even more aggressive immune response, resulting in persistent airway inflammation that may result in airway obstruction. Increased sputum may further obstruct airways, and the combination of which may result in severe asthma. This may further progress to bronchiectasis.

Bronchiectasis is the result of prolonged and untreated airway inflammation caused by infections, which in our case is aspergillus fumigatus. This inflammation gradually damages cells lining airway walls causing them to become dilated and scarred, or thickened. This is sometimes referred to as airway changes or scarring.^8,10

Mucus becomes thick and difficult to move due to “structural abnormalities” of airway cells. This mucus can further block airways, thereby causing flare-ups of bronchiectasis and severe asthma.^3,8,10

Diagnosis

Lab and allergy testing can determine if you have a sensitivity to aspergillus fumigatus. This is marked by elevated aspergillus fumigatus IgE, along with elevated serum IgE and eosinophil levels. Chest x-ray may show signs of bronchiectasis and mucus plugging. Aspergillus fumigatus will be present in the sputum of about two-thirds of patients with ABPA.^1-4

Pulmonary function testing may show airflow obstruction that is at least partially reversible.

Treatment

High dose inhaled steroids reduce airway inflammation, and prevent asthma symptoms, or to at least make them less severe when they do occur. Systemic corticosteroids are sometimes needed.⁵

Leukotriene antagonists like Singulair may prove helpful. As usual, all asthmatics should have access to rescue medicine, like albuterol, at all times. Antifungal medicines may also help reduce symptoms of both asthma and sinusitis.⁵

Various other asthma and COPD medications may help obtain asthma control. Occasional hospital admissions may also be necessary.⁵

Research

Aspergillus fumigatus was first recognized by scientists in 1954. Researchers are arduously working to learn more about ABPA, why it develops in some and not in others, and what the link is between asthma, sinusitis, and ABPA. This should result in better methods of recognizing and diagnosing it, and better treatment options aimed specifically at this subgroup.¹⁰

Early diagnosis and treatment is important. The disease is progressive over time, and early recognition, diagnosis, and aggressive management can slow the progression. Ideally, the disease should be diagnosed prior to the development of bronchiectasis, as this can further complicate treatment.^{9, 10}

Conclusion

Now that researchers are aware of this asthma subgroup, they are working to educate physicians about it and encouraging them to be wary of signs and symptoms of ABPA in any patient with asthma and atopy.